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Indian and East Asian (EA) monsoon subsystems are driven by different lower-boundary thermal forcing associated with land-ocean configuration and topography.

Examination of the different characteristics of the annual variability of the two subsystems may provide useful insight to understand how tectonic forcing and solar orbital forcing affect monsoon circulation.

The differences in the annual cycle are attributed to the effects of differing land-ocean configuration on atmospheric response to the annual solar forcing, which resembles the effects of the external (tectonic and orbital) forcing on paleo-monsoon variability.

Are factors that determine annual cycle of monsoon also operate on interannual time scale?

Study of the different response and feedback of the Indian and EA monsoons to ENSO and warm pool conditions would shed light on the paleo-monsoon variability over the South China Sea and over the Arabian Sea.

Observations have revealed that the year-to-year variations of the Indian and EA-WNP summer monsoons exhibit strikingly different spatial and temporal structure and teleconnection patterns (Wang et al. 2001a).

The pattern has an SIO anticyclone (AC) in the developing year of El Nino and a WNP AC in decaying ElNino. El-Nino forcing alone cannot account for: 1) the amplification of the SIO AC;or 2) the maintenance of the WNP AC. These features result from local air-sea interactions and the impacts of the annual cycle.

The factors that control monsoon intensity may be classified as two groups: The forcing external to the coupled atmosphere-ocean-land system (tectonic forcing and solar orbital forcing) and the forcing internal to the coupled climate system, such as (remote) El Nino/La Nino, local monsoon-ocean interaction, land-atmosphere interaction and extratropical influences (ice or snow cover).

The mechanisms operating on the annual and interannual time scales are dominated, respectively, by the external and internal forcing.

The differences between the Indian and East Asian monsoon is essentially determine by the relative strengths of the external versus internal forcings.

The robust coupling between the East Asian and Australian monsoon on both the annual and interannual time scales is essentially established by tectonic forcing. Thus, the increase in solar procession could enhance both the Indian summer monsoon and the East Asian winter-Australian summer monsoons.

El Niño has little influence on the Arabian Sea summer monsoon, but considerable impacts on the South China Sea monsoon (about 10% on average and 40% in strong events), suggesting that drastic changes in the Pacific thermal conditions could remarkably alter the East Asian-Australian monsoon intensity.

The leading mode (38% of total variance) represents enhanced precipitation along the EA subtropical front, primarily associated with decaying phases of El Ninos (and after 1990 its reversed pattern links to developing phase of El Nino).

The response of the EASM to El Nino and La Nina forcing is nonlinear.

The second mode (11.3% of the total variance) is associated with developing phases of the El Nino and La Nina events and the third mode (7.4% of the total variance) links partially to the NINO4 warming.

The leading mode of the EA-WNP summer monsoon represents enhanced precipitation along the EA subtropical front, primarily associated with decaying phases of El Ninos (and after 1990 its reversed pattern links to developing phase of El Nino).

H How are the teleconnection (the PJ and circumglobal teleconnection) modes associated with Asian summer monsoon excited and maintained? Are those modes intrinsic to the low frequency variability of the boreal summer mean states?

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What is the predictability of the EA-WNP summer monsoon during the years when ENSO is in a near normal state?

· How does the monsoon-warm ocean interaction affect the predictability and prediction of the seasonal mean rainfall?

· What is the potential and practical predictability of the EA and WNP summer monsoon?

· What are the impacts of the ISO on the seasonal mean climate forecast?

Interdecadal variability

· What is the dominant mode of the Interdecadal variation of the EA-WNP monsoons? What give rise to this variability?

· Are the interdecadal variations in the EA-WNP region linked to that over the ISM? If not how different they are and why they are different?

Conceptual spectrum of monsoon variability on the annual to tectonic time scale. The periods of individual spectral peaks are labeled. Relative concentrations of variance at these periods are unknown. The two black peaks at the 41- and 23-ky periods indicate the Earth-orbital periods, which account for nearly all variability in incoming solar radiation.